My old 98' Sienna became the warmest place for a cat in the neighborhood. It seems that while the cat was trying to get on top of the engine he decided to help climb the engine grabbing the spark plug wires until the inside of the cables was visible. The car started a few weeks ago to suddenly shut down so I thought that might be related to the wires or a faulty fuel pump.
I changed the wires with a Denso set i got online. Once done, started the engine and the car was idling like a diesel truck, super-rough and after a few minutes will just choke and will shut down. After some research, decided to change fuel pump which was also failing lately but had no chance to it. Did so, got it replaced but the car was still running really rough. I got some ignition coils from Amazon and once I got them, changed them but problem did not went away. I was getting P300,301,303,305 codes which was driving me crazy after changing the spark plug wires and ignition coils. Looked for vacuum leaks but nothing wrong there. Took the new wires off and reinstall them again like 2 o 3 times. Stayed the same.Tried to start it several times but the car refused to start. It was like when you have a manual transmission car that is chocked. Called my mechanic and he told me that was going to come home to check it.

Removed the wires again and put them the way are supposed to go as per the diagram I got from the internet just to make sure that i was not leaving anything disconnected or connected backwards and wait for the mechanic to come and look at it. For some reason, decided to disconnect both terminals from the battery for an hour while having lunch hoping that doing that will reset the computer just in case. Came back, started the car for a last time before closing the hood and storing my tools and guess what?

Started right away, no hesitation, was not running rough and was back to normal. No check engine light which was always on after running for a while due to a oxygen sensor on the exhaust that needs to be changed but it seems that disconnecting the battery did reset and erased everything that was stored on the computer memory even after I had deleted the codes previously with a scanner that i got for Christmas (recommended by Scotty!).

Scanner said that there were no more error codes at all. Took it for a spin around town without any issues and stopped to get some gas. Kept driving for half an hour and checking the scanner for any codes but nothing was coming back and the car was running like a champ. I hope this tip can save you some headaches and money.